3, 4-thiolanedithione



Patented July 18, l1.950 t r u Nireo .STATES PATENT oFiFiiC-E l l y v -a515,92r:1 I i V3,4411?'n'IoLAlxuinfi'rIiIoNii' l v Sigmund J."=Iiu`ka!siewicz, Woodbury, N...J., as-

si'gnor to Socony-Vacuum Oil.` Company, Incor'fporated,va corporation oNew ,York No Drawing. spontanen Jannaryio, 1947,

Serial N0. 7215453 This invention relates to a new'composition foi matter vand `method for preparing thel saine. More particuiarly the present invention isdirested to a new l organo-sulfur compound and Yto thelsynth'esis` thereof said compound being char-s l aoterized by the hfeiiifiirical formula Cil-Liss` :and a rboiling"point oi 1120-12?Qata'pressure of 2 millimeter-s of mercury.`

'-It has been discovered, 'in accordance with the presentinvention, that a 'new anduseful organic compound can beobtained by vacuum distiilation o'f ltliiophene tais' which 'are produced 'by vreacting certain hydrocarbons with sulfur, as hereinafter described.V I

Processes 'for preparing `the Ittiophene tars in excess 'of1ab'ou1'f2i5'0d Vmixing 4the preheated slililiur rand preheated hydrocarbozi mixture, maintaining the 'temperature of the mixture at a temperature in excess of about v450" Cjfor a period-.of `time of at Vlwea'stool second and `reducing the temperature fof "the 1n''ii{t1i1'-e`'v to' :less than about 450 Along withthiophene tar and thi'ophen'e, hydrogen sulfide fand `sinall "amounts of carbon rtdis'uliide` are-also Aforrriedin the process.

While .relatively large quantities of sulfur are employed ain- .preparing `the thiop'hene tarsfsul- 'fur :is,i.-nevertheiess,.one ofthe 'least expensive :and inost noneeriticalof chemical: reagents. It has been .ioundiinv4the operation yof this :process that the relative` lj ziroportions`of 'sulfur and hydrocarbon Amaterialiin the .charge 4may be varied over willie' limits. .'Ifo'o inuch sulfur, however, results in poor eiiiciency in suliuiutiliz'ation -iier pass and ffav'ors the-complete sulfuriz'ation of hydra carbon material 'to carbon disulfide. Yet, too low aproporltioniof sulfur lowers :the conversion per passanti the ultimate yield vby l'increasing the overall-thermal degradation of hydrocarbon material. Generally speaking, fb'est :results `are obs claims. (o1. 2604-329 tained iusingV .a weight ratio fof .sulfur to 4l'riydrocarbon :materialfvaryinfg between' about 0.5' and .about 4.0.,although when Vbultenes .and bu'tadieries constitute the bulle-of the `hydrocarbo'n charge, ItheE lower limit ofthe weight ratio may be lower it liti-0.5. mit should be observed, however, that i leconomical*operation of the process, it is preifeilr'ed not to use afhydroc'arbon charge consistiiig predominantly of -butadien'es because'oi their `tendency to polymerize under the conditions' lf 'the-process.

The selectivity of 4the reaction involved `in fthe process fori thepreparationof thiophene tarsand thiophene depends primarily upon two -variabl`es; 'nainely,th'e re'aetion temperature at 4-vvhi'ol'i tithe iioi-'iiial aliphatic hydrocarbon `or hydrocarbons are contacted with sulfur, and the reaction time or fthe' time during which contact between the reactants -isnialntaind at the reaction temperature.

The limits offoperating temperature-areied between-the kinetics fof ytl'ie'desireci yreaction fand lthe' kinetics of possible side reactions. "It has lbee'ri 'found, 4in this connection, that the reaction 'temperature 1may vary-between about 450 and about' 17'69" YC. and preferably between 'about -540i about @551 or when' bntane 'iis 'the pie dorniiiant* ,drocarbon reacting in "the rcharge fairdlbtw'eeii'fabolitll 5C. fand. about "59`'1C. Wlieil butenesiandbutadienes are the ypredominant hydrocarbon reactantsin the charge.' Below the lower limitl of the temperature range (about 450 \C.), the reaction -is `so Slow as to require 'alarge throughput of sulfur and a higher ratio of y-hyrt'icarbon irecycle 1lfor a-xed amount of fend product, thereby detracting from the `economics oi the operation; "Above the upper limit of the temneratureirange, ytlie secondary vlreaction of ieg- -radatiori .of hydrocarbon material in the charge ftalz'es niii-'eoedence, thereby decreasing the yield LVof desired broduet Jin-addition to this, high temperatures; fa-vor the 'formation of `carb on disulfide. Itmust be noted, also, that at these high tern-- literatures-corrosion problems are at a maximum, cori-esisti` increasing aperceptibly with increasing teiiiperature.

Itfilfias also been foundgin connection with this process, that the optimum reaction timedepends uneny the temperature employed. v-In general, other variables remaining constant, the vlovver `the temperature, the longer the-'reaction time. The reaction or y'c'zentact time `andthe reaction temperatureare somewhat iixed, one `in relation to the other, by -th'e degree 'of degradation o'f the hydrocarbonniaterial in .the charge and by the etieeteo'i formation `of .undesirable products which may-be tolerated.. Ilhus', too long' a contact-'tima 3 at high temperature results in severe cracking of the hydrocarbon material in the charge. The reaction proceeds with extreme speed, the only apparent limitation being the rapidity with which heat can be sup-plied to the reaction mixture. The reaction is highly endothermic, requiring by experimental measure approximately 28,000 calories per gram` molecular weight of thiophene produced from normal butane. The lower limit of the range of reaction time is xed, therefore, by the engineering problem of heat transfer and by mechanical limitations such as allowable pressure drop across the reactor. Relatively long reaction times at temperatures in the neighborhood of the lower limit of the temperature range results in lower yields of thiophene and increased yields of thiophene tar. Too short a reaction time, however, at temperatures in the neighborhood of the lower limit of the temperature range results in insuilcient reaction. Accordingly, it

.has been found that for best results the time of `reaction is fixed by the reaction temperature.

In view of the foregoing, the criteria to be used in determining optimum operating temperatures ,within the range of 450 C. to 760 C. depend on the degree of conversion desired commensurate with operating costs, such as heat input and `equipment cost, bearing in mind that within limits, the shorter the reaction time, and accordingly the higher the temperature, the larger the :arnount of end product which can be realized from a unit of given size per day.

While the relationship between the temperavture of reaction and reaction time is not peculiar Jtical charge rate, it has been found that the lowest practical limit of the time of reaction is of the order of 0.01 second at about 760 C. The upper practical limit of the reaction time, other variables remaining constant, will correspond to the lower limit of the reaction temperature and may be of the order of several seconds.

, Separate preheating of the hydrocarbon reactant and sulfur and quenching of the reaction mixture are necessary for achieving the somewhat close control of the reaction time at a given reaction temperature. This is very important in the specic reaction products, thiophene and thiophene tars. It is suspected that a number of reactions occur upon contacting the hydrocarbon reactant and sulfur. In this connetcion, the following should be noted: cracking of the hydrocarbon reactant, destroying the 4-carbon atom chain structure (said 4-carbon atom chain structure being a prerequisite for the formation of thiophene), formation of thiophene tars high in sulfur and formation of carbon disulfide. These "reactions compete one with another. It has been found that the rates of the formation of lighter carbons and of the formation of carbon disulfide are somewhat slower than those required for the formation of thiophene and thiophene tars. Accordingly, proper control of the reaction time at a given reaction temperature, achieved by separate preheating, mixing, heating at a given temperature for an increasing period of time, and quenching is necessary to produce high yields of thiophene and thiophene tars with limited yields of carbon disulfide, coke-like materials, and fixed gases, due to a limited decomposition of the hydrocarbon product. The rate of the reaction producing thiophene tars is fairly close to that required for the formation of thiophene, and the yields of thiophene tars and of thiophene are approximately the same.

In carrying out the process for preparing thiophene tars, it is essential to preheat the reactants separately. Heating the hydrocarbon material and sulfur together is undesirable in that heavy tars are produced and these are subsequently cracked in the reactor, causing undue coke formation. Tests have shown that when the reactants are heated together up to temperatures within the aforementioned reaction temperature ranges, tar formation is favored, as is subsequent cracking thereof, with the result that the reaction zone is eventually filled with a heavy carbonaceous deposit. Therefore, it is essential to preheat each of the reactants separately, that is, the hydrocarbon mixture or mixture of hydrocarbons and sulfur to such temperatures that when they are brought together under proper conditions of flow, a temperature within the reaction temperature range is achieved before effecting contact between them. In practice, this is eected ordinarily by separately preheating each of the reactants to temperatures within the reaction temperautre range.

After separately preheated hydrocarbon reactant and sulfur are mixed and allowed to react for the reaction time indicated by the operating temperature, the temperature of the reaction mixture is immediately lowered to below about 450 C., in practice appreciably below 450 C. in order to avoid over-reaction in the system after leaving the reactor. This may be achieved suitably by spraying the product leaving the reactor with a liquid.

In this process the reaction is effected preferably at atmospheric pressure or under sufficient pressure to cause the flow vof the reactants through the reactor and auxiliary system under the desired reaction conditions. Tests have shown that the yield per pass and ultimate yield of thiophene decreases with increasing pressure. However, even at appreciable pressures, thiophene and thiophene tars are, nevertheless, produced in substantial amounts. v

Vacuum distillation of the above described thiophene tars is a destructive distillation process in which the charge probably disuldes, polysulfldes, etc., is decomposed during the heating process into distillable liquids and hydrogen sulfide. A specific embodiment of the present invention involves destructive vacuum distillation of the original tar and subsequent vacuum fractionation of the distillate so obtained to yield two distinct fractions, a lower boiling material which has been further described in copending application Serial Number '721.454, filed January 10, 1947, and a higher boilingl material constituting the new compound of this invention.

During the course of the aforesaid vacuum distillation, hydrogen sulfide isvevolved, giving rise to frothing and bumping of the tar. These undesirable conditionsv have been overcome, however, by resorting to any one of several modifications. Smoother operation is realized by locating a capillary tube inthe distillation vessel so that its lower end is located below the surface ofthe boiling tar and directing Karstream of Ainert gas, such. as carbon dioxide,v nitrogen, .or the like, 'through .the tube and 4thus through the boiling tar. Another means involves first evacuating the distillation vessel at room temperature to de-gas the tar therein and thereafter slowly increasing `the temperature .of the tar. Hydrogen sulfide evolved from .theftar ,during the distillation is readily. removed vby `scrubbing the evolved gases .by passing. .through-towers filled with acid-,absorbing 5mediasuchas soda lime, sodium hydroxide pellets, etc. This absorption of hyrdogen sulfide .protects the mechanical moving parts of the `pump vused Lto obtain fthe desired .vacuum and -hence vis highly desirable. ejector system is used to obtain vacuum, the preliminaryabsorbing step vmay be omitted, since in this case .the :hydrogen sulde will be exhausted totheatmosphere.

It 'has been found that .maximum distillation efficiencycan be attained by keeping the pressure .below l millimeters and preferably below 2 millimeters of mercury. If the .pressure is permitted to rise to the .order of 10 millimeters ol mercury, vthe temperature vmust necessarily be increased for distillation `to occur at a reasonable ratewarid ultimatelyV uthe lrate of decomposition with evolution of hydrogen sulfide becomes too rapid'to maintain anappreciable vacuum. When the temperature lof .the initial distillation rises to :the neighborhood .of 250 C., the tar has a tendency to lpolymerize and coke. Accordingly, the. temperature of lthe initial distillation should be maintained between about 150 C. and about 250 V(Land .preferably 4between about 175 C. and about. 190 C'. to .attain a maximum yield of red oily distillate. Under the above specified condin tions of .temperature and pressure, approximately -50 `per cent .of the initial charge of thiophene tar is distillable.

Subsequent vacuum fractionation of the red oily distillate is carried out at pressures below 10 millimeters of mercuryY and preferably at Ll millimeters oimercury .or below. Such redistillation yieldstwo distinctfractions, a low boiling fraction (40451C. at .2 millimeters) constituting 60-85 per cen-t `of the `initial distillate and a high boiling fraction `(1Z0-125 C. at 2 millimeters) constituting: approximately 1'5-40 per cent of the initial distillate.

Having described in a ygeneral way the nature .0f this invention, the following example will serve as an illustration without limiting the same:

Example A mixture containing` 30 .per cent `by volume of LS1-butadiene and, 70 per cent by volume of normal .butano was `charged into a vpreheater at a rate .of `grams per minute and heated to a temperature of 590 C. Sulfur was charged to a separate .preheater at a rate of 28 grams per minute and `heated `to a temperature of 590 C. The ftwostreams were sent through a mixing nozzle and then through a ballied tube reactor constructed `of 27 per cent chromium stainless steel, maintained at a temperature of 650 C. The reaction product was quenched with a water spray passed through a `small Cottrell precipitator to remove .tar mist and scrubbed through a hoil countercurrent caustic tower. Liquid product was` condensed and separated in .a water cooler and ice trap and .theresidual gas was metered. Of the hydrocarbon. material charged, 49 per cent was converted `.to liquid product and tar.

However, if a steam Fractionation .of a portion of the liquid `.prod-uct after the removal of C4 hydrocarbons and lighter constituents showed .the .following :composition:

Thiophene tar, such as :the tar `.obtained vaccording to the above described procedure', was found to have the following characteristics:

Average weight per cent sulfur 56.7 Average molecular weight V281 Specific gravity lil/65 F'. 1.4'6'0 Weight per cent insoluble in benzene "7.5 Weight per cent free sulfur 0.09 Weight per cent sulfur as 'SI-I nil Viscosity (S.U.V. at 210 F.) 46

One hundred parts by weight of such thiophene tar were vacuum-distilled in a distillation vessel immersed in a heating bath. While warming the tar, a stream of nitrogen was bubbled through'the heavy liquid until the' tar was de-gassed. A scrubbing tower for removal of hydrogen sulde and a Dry Ice-acetone condenser for removal of light liquids were connected in series before the vacuum pump. The bath temperature was allowed to rise slowly and` then was maintained Aat 175-200 C. A pressure of 1 millimeter of lmercury was initially obtained 4but this gradually rose upon prolonged heating of the .tar untilamaximum pressure of 10 millimeters of mercury was reached. The product consisted of 226 :parts by weight of a red oil distillate boiling between C. and C. The yield .oi said distillate, based on the weight of tar, was 45.3 per cent.

yThe red oil was then vacuum-fractionated at a pressure of 2 millimeters of mercury, whereupon the following fractions were obtained:

C yBoiling Wiz Per Cent Fraction A Point Range (Basedon at 2 mm. .Original Tar) Material boiling with the range fof fraction .2 constitutes the new compound of this invention and was shown to have the following properties:

Molecular weight 157 Carbon per cent 34.46 Hydrogen do 2.60 Sulfur do y62;() Molecular formula C4H4S3 Refractive index 20 C 1.70 Specific gravity 25 C./25` C 1.446

Color Deep red The new organo-sulfur compound obtained in. accordance with the above described process .is useful as an intermediate for the preparation of pharmaceuticals, as a mineral oiladditive, in the. manufacture of insecticides, in the compounding of rubber and as a flotation agent. Tests. have shown that the compound ofnthis invention .is

particularly applicable as a flotation agent in aqueous Isolution for the separation of suldes from siliceous gangues. A saturated aqueous solution of the compound gave a contact angle of about 70 degrees with galena or covallite, while zero angle was observed with quartz. Separation of'these suliides from quartz can, therefore, be readily accomplished using the compound isolated in accordance with the above procedure as a soluble collector.

I claim:

1. A method for making A-thiolanedithione, comprising separately preheating sulfur and a C4 hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes to temperatures such that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature between about 450 C. and about 760 C., mixing the preheated sulfur and the preheated hydrocarbon in a proportion wherein the weight ratio of sulfur to hydrocarbon is below that favoring complete sulfurization of the hydrocarbon to carbon disulde, reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C.-and about '760 C. to yield a mixture containing a tar, immediately reducing the temperau ture `off the mixture containing said tar to a temperature of less than 450 C., separating the tar from said mixture, vacuum-distilling said tar y at a pressure below about l millimeters of mern curyand a temperature between about 150 and about 250 C., redistilling the resulting initial distillate under reduced pressure at a tempera ture .corresponding to that within the range 1Z0-125 C. at a pressure of 2 millimeters of meicury and collecting the resulting distillate.

2. A method for making 3,4-thiolanedithione, comprising separately preheating sulfur and a C4 hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes to temperatures such that combining said sulfurand said hydrocarbon will give a reaction mixture Y having a temperature between about 450 C. and about '760 C., mixing the preheated sulfur and the preheated hydrocarbon in a proportion wherein the weight ratio of sulfur to hydrocarbon is below that favoring complete sulfurization of the hydrocarbon to carbon disulfide, reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C. and about 760 C. to yield a mixture containing a tar, immediately reducing the temperature of the mixture containing said tar to a temperature of less than 450 C., separating the tar from said mixture, vacuum-distilling said tar at a pressure below millimeters of mercury and a temperature between about 150 C. and about 250 C., re-distilling the resulting initial distillate at a pressure below about 10 milli meters of mercury and recovering the distillate having a boiling point within the range corre sponding to 120-125 C. at a `pressure of 2 millimeters oi mercury.

3. A method for` making 3,4-thiolanedithione, comprising separately preheating sulfur and a C4 hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes to temperature such` that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature between about 450 C. and about 760 C., mixing the preheated sulfur and the preheated hydrocarbon in a pron portion wherein the weight ratio of sulfur to hydrocarbon is below that favoring complete sulfurization of the hydrocarbon to carbon disulfide, reacting said preheated sulfur with said preheated hydrocarbon at a vreaction temperature varying between 450 C. and about 760 C. to yield a mixture containing a tar, immediately reducing the temperature of the mixture containing said tar to a temperature of less than 450 C., separating the tar from said mixture, vacuum-distilling said tar at a pressure below 2 millimeters of mercury and a temperature between about C. and about C., re-distilling the resulting initial distillate at a pressure below 10 millimeters of mercury and recovering the distillate having a boiling point within the range corresponding to 12o-125 C. at a pressure of 2 millimeters of mercury.

4. A method for making 3,4-thiolanedithione, comprising separately preheating sulfur and a C4 hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes to temperatures such that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature between about 450 C. and about '760 C., mixing the preheated sulfur and the preheated hydrocarbon in a proportion wherein the weight ratio of sulfur to hydrocarbon is below that favoring complete sulfurization of the hydrocarbon to carbon disulfide, reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C. and about 760 C. to yield a mixture containing a tar, immediately reducing the temperature of the mixture containing said tar to a temperature of less than 450 C., separating the tar from said mixture, vacuum-distilling said tar at a pressure below 10 millimeters of mercury and at a temperature between about 150 C. and about 250 C., re-distilling the resulting initial distillate at a pressure of about 2 millimeters of mercury and recovering a fraction having a boiling point of from about 120 C. to 125 C. at said pressure.

5. A method for making 3,4-thiolanedithione, comprising separately preheating sulfur and a C4 hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes to temperatures such that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature between about 450 C. and about 760 C., mixing the preheated sulfur and the preheated hydrocarbon in a proportion wherein the weight ratio of sulfur to hydrocarbon is below that favoring complete sulfurization of the hydrocarbon to carbon disulde, reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C. and about 760 C. to yield a mixture containing a tar, immediately reducing the temperature of the mixture containing said tar to a temperature of less than 450 C., separating the tar from said mixture, heating said tar under conditions of temperature and pressure to bring about fractionation thereof and thereafter recovering the distillate having a boiling point within the ranjge corresponding to 1Z0-125 C. at a pressure of 2 millimeters of mercury.

G. A method for making 3,4-thiolanedithione, comprising separately preheating sulfur and a C4 hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes to temperatures such that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature between about 450 C. and about 760 C., mixing the preheated sulfur and the preheated hydrocarbon in a proportion wherein the weight ratio of sulfur to hydrocarbon is between about 0.5 and 4, reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C. and about 760 C. to yield a mixture containing a tar, immediately reducing the temperature of the mixture containing said tar to a temperature of less than 450 C., separating the tar from said mixture, heating said tar under conditions of temperature and pressure to bring about fractionation thereof and thereafter recovering the distillate having a boiling point within the range corresponding to 1Z0-125 C. at a pressure of 2 millimeters of mercury.

7. A method for making 3,4-thiolanedithione, comprising separately preheating sulfur and a C4 hydrocarbon selected from the group consisting of normal butane, normal butenes, and butadienes to temperatures such that combining said sulfur and said hydrocarbon will give a reaction mixture having a temperature between about 450 C. and about '760 C., mixing the preheated sulfur and the preheated hydrocarbon in a proportion wherein the weight ratio of sulfur to hydrocarbon is between about 0.5 and 4, reacting said preheated sulfur with said preheated hydrocarbon at a reaction temperature varying between 450 C. and about 760 C. tc yield a mixture containing a tar, immediately reducing the temperature of the mixture containing said tar to a temperature of less than 450 C., separating the `tar from said mixture, vacuum-distilling said tar at a pressure below 10 millimeters of mercury and at a temperature between about 150 C. and

yabout 250 C., re-distilling the resulting intial at said pressure.

8. As a new composition of matter, 3,4-thiolanedithione, characterized by the structural formula:

SIGMU'ND J. LUKASIEWICZ.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,102,564 Bonstein Dec. 14, 1937 2,410,401 Coffman Oct. 29, 1946 2,450,659 Hansford Oct. 5, 1948 Certificate of Correction Patent No. 2,515,927 July 18, 1950 SIGMUND J. LUKASIEWICZ It is hereby certied that error appears in the printed specificationl of the above numbered patent requiring correction as follows:

Column 3, line 61, for connetcon read connection; line 70, for the word carbons read hydrocarbons; column 4, line 33, for temperautre read temperature and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oce.

Signed and sealed this 6th day of March, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

8. AS A NEW COMPOSITION OF MATTER, 3,4-THIOLANEDITHIONE. CHARACTERIZED BY THE STRUCTURAL FORMULA: 